Ch 21 notes - Chemistry 140C Spring 2009 (K. Albizati)...

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Chemistry 140C Spring 2009 (K. Albizati) 1 Chapter 21 Amines and Their Derivatives Amines are the nitrogen analogs of alcohols. The amine functional group is quite prominent in pharmaceutical and agricultural chemicals and is important in the polymer industry. Structure and Physical Properties Amine nitrogen is sp 3 -hybridized and tetrahedral: The nitrogen non-bonded pair acts like a substituent --- the geometry is tetrahedral around nitrogen and the bond angles are all around 109 o . But if you only consider the atoms, the geometry is pyramidal .
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Chemistry 140C Spring 2009 (K. Albizati) 2 Unlike carbon, sp 3 -hybridized nitrogen is not rigid and it undergoes a rapid inversion at room temperature: It is like an umbrella flipping inside-out and similar to the inversion of configuration which occurs in an S N 2 reaction. Amines form much weaker hydrogen bonds, in general, than alcohols. Hence, the boiling points of amines are not as high as the structurally- corresponding alcohols and are intermediate between alkanes and alcohols: Amines tend to have a fishy odor and the low molecular weight amines are quite pungent. Nomenclature All the usual IUPAC rules are followed; the suffix –amine is added to the name at the end and the position of the amino group must be specified.
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Chemistry 140C Spring 2009 (K. Albizati) 3 For 2 o and 3 o amines , the largest alkyl substituent is chosen as the parent and the other alkyl groups on nitrogen are named as substituents with the prefix N- to denote that they are attached to nitrogen: Because the amine functional group has the lowest priority in naming (p 857) it is often named as a substituent on more highly functionalized molecules: Finally, some important common names:
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Chemistry 140C Spring 2009 (K. Albizati) 4 Acidity of Amines Amines are much less acidic than alcohols: To completely deprotonate an amine, you must use a very strong base like an alkyllithium: Recall that LDA is an important base in organic chemistry --- it is strong enough to deprotonate carbonyl α -hydrogens and it is quite hindered, so it has negligible nucleophilic properties. Basicity of Amines
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This note was uploaded on 08/04/2009 for the course CHEM CHEM 140C taught by Professor Finn during the Spring '08 term at UCSD.

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Ch 21 notes - Chemistry 140C Spring 2009 (K. Albizati)...

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